A Certificate of Analysis (COA) is the minimum verification document any researcher should request before working with a peptide obtained from a commercial source. Yet it is also the most frequently misunderstood. Vendors routinely issue COAs that are technically present but analytically meaningless — and knowing the difference is the only practical tool available to researchers operating outside regulated pharmaceutical supply chains.
This entry covers every field a legitimate COA must contain, explains what the numbers mean, and identifies the specific patterns that should immediately disqualify a source from consideration.
What a COA Is — and What It Isn't
A COA is a document reporting the results of analytical testing performed on a specific batch (lot) of a chemical substance. For research peptides, the relevant tests are High-Performance Liquid Chromatography (HPLC) for purity and Liquid Chromatography–Mass Spectrometry (LC-MS) for identity confirmation.
A COA is not a regulatory approval. It does not certify that a substance is safe for any use, approved by any medicines authority, or manufactured under GMP conditions. It is purely an analytical report — and only as trustworthy as the laboratory that produced it.
The Seven Fields Every Valid COA Must Include
1. Compound Identification
The COA must state the full chemical name of the compound — either the IUPAC systematic name or the accepted International Nonproprietary Name (INN) — alongside the CAS Registry Number. Vague descriptions such as "research peptide" or trade names without a CAS number are a red flag. The CAS number is an unambiguous identifier; you can verify it independently against public databases such as the NIST WebBook or PubChem.
2. Lot / Batch Number
The lot number on the COA must match the lot number on the product packaging you actually receive. Generic COAs — those not tied to a specific production lot — have no verification value whatsoever. A vendor who cannot or will not supply a lot-specific COA is offering no analytical assurance at all.
3. HPLC Purity Result
High-Performance Liquid Chromatography separates the components of a sample and reports the relative abundance of each as a percentage of the total chromatographic peak area. The target compound should represent ≥98% of total area. This is the research-grade threshold consistently cited across independent analytical laboratories working with synthetic peptides.
Purity results between 95–97% indicate a meaningful level of impurities — potentially including truncated sequences, oxidised residues, or deletion products — that would compromise the validity of any research using the sample. Results below 95% are simply unacceptable for any serious research application.
4. LC-MS Identity Confirmation
Liquid Chromatography–Mass Spectrometry confirms the molecular identity of the dominant compound by comparing its observed mass to the theoretical molecular weight of the declared peptide. The observed mass should match within ±0.02 Da for small peptides (under approximately 3,000 Da) or within the instrument's mass accuracy specification for larger molecules.
LC-MS identity confirmation rules out substitution fraud — the practice of supplying an entirely different compound, often a cheaper or more readily available analogue, labelled as the target peptide. HPLC alone cannot catch this; it can only tell you that one dominant compound is present, not which compound it is.
5. Independent Testing Laboratory
The laboratory that performed the analysis must be independently identifiable. Its name, address, and ideally a report reference number should appear on the COA. You should be able to find this laboratory through a simple web search and confirm it operates independently of the vendor.
A COA issued by the vendor's own in-house laboratory has no independent verification value. The vendor is, in effect, marking their own homework. This is one of the most pervasive problems in the research peptide space, and it is not always disclosed prominently.
6. Test Date
The analysis date must be present and must be relatively recent. A COA from two years ago applied to a batch produced last month tells you nothing about the current batch. Equally, a lot number implying recent manufacture but paired with a years-old test date is a clear inconsistency warranting scrutiny.
7. Method Specification
The analytical method used for purity determination (HPLC conditions: column, mobile phase, gradient) and for identity confirmation (LC-MS conditions: ionisation mode, mass range) should be stated or referenced. This is not always present in summary COAs, but its absence means the results cannot be critically evaluated or independently reproduced.
Red Flags: When a COA Should Be Rejected
| Pattern | Assessment |
|---|---|
| HPLC purity below 98% | Unacceptable — impurities exceed research-grade threshold |
| No CAS number or vague compound name | Identity unverifiable — reject |
| No lot number, or lot doesn't match packaging | COA is not for this batch — meaningless |
| Lab = vendor's own laboratory | Not independent — no verification value |
| Lab name not findable independently | Unverifiable laboratory — treat as void |
| No LC-MS identity data | Identity unconfirmed — substitution undetected |
| Test date predates batch production | Temporal inconsistency — reject |
| Purity ≥98%, independent lab, lot-specific | Minimum requirements met — proceed with scrutiny |
What a Valid COA Does Not Guarantee
A COA meeting all the above criteria confirms that a specific lot, at the time of testing, contained the declared compound at acceptable purity. It does not confirm:
- Sterility — HPLC and LC-MS do not detect microbiological contamination.
- Endotoxin absence — Bacterial endotoxins require a separate limulus amebocyte lysate (LAL) test.
- Storage integrity — Degradation occurring during shipping or after receipt is not reflected in the original COA.
- Regulatory compliance — A valid COA does not mean the substance is legal to import, possess, or use in your jurisdiction. See the country directory in this compendium for relevant national competent authority guidance.
- Safety for human use — This point cannot be overstated. No analytical document substitutes for medical supervision.
How to Request and Verify a COA
Before any order, explicitly request the lot-specific COA for the exact lot you will receive. If a vendor cannot provide a lot-specific COA with an identifiable independent laboratory, that is a definitive answer about the level of quality assurance they offer.
Once you have the COA, verify the laboratory independently. Search for its name and contact details. Check whether it is accredited (ISO 17025 accreditation is the gold standard for analytical laboratories; its presence is a positive signal, though its absence does not automatically invalidate results). Cross-reference the CAS number against PubChem or the NIST WebBook to confirm the declared compound matches its stated identity.